Yarns prepared from nylon fibers, such as nylon 6 and nylon 6,6, are commonly used to prepare tufted carpets. Because of cationic charged groups on nylon fibers, such carpets are subject to staining by acid-functional agents (or “acid dyes”), such as those contained in flavored beverages (i.e., Kool-Aid®) or coffee. Such stains are often permanent and over the years much effort has been put into methods of preventing staining by these common staining agents.
To reduce the propensity of nylon fibers to stain with acid dyes, various stainblocker treatments have been used. These stainblocker treatments normally function by blocking the negative charges on the fibers so as to prevent acid dyes from attaching to the fibers. Generally, the stainblocker treatments will leave a net negative charge on the nylon fiber surface to further repel staining by acid dyes. Sulfonated aromatic aldehyde condensation polymers (“SAC”) and methacrylate type anionic polymers are commonly applied to acid dyeable nylon fibers as stainblockers. Typical stainblockers are disclosed, for example, in U.S. Pat. Nos. 4,501,591, 4,592,940, 4,680,212, 4,780,099, 4,865,885, 4,822,373, 4,875,901, and 4,937,123. The disclosures of each of these patents are incorporated herein in their entireties by this reference.
Acid dyes will not normally stain cationic dyeable fibers. Cationic dyeable nylon fibers have free negative charges and will exhibit resistance to anionic colorant stains. Because of this inherent stain resistance, cationic dyeable fibers have experienced an increased usage in recent years, particularly in commercial carpets used for schools, offices, healthcare facilities and in the food service industry.
In both acid dyeable nylon fibers treated with a stainblocker and in cationic dyeable fibers, acid dyestuffs spilled on the fibers can be removed by rinsing or extracting with water. However, disperse (or uncharged) dyestuffs will still stain nylon fibers treated with stainblockers, as well as cationic dyeable nylon fibers. Disperse dyes that will commonly come into contact with nylon fibers in use are iodine (such as in a Betadine, which is a 10% povidone iodine solution made by Purdue Pharma, LP) and turmeric (such as in mustard products). The colorants contained in Betadine and mustard are neutrally charged and are accordingly unaffected by a charge/charge repulsion mechanism. Due to their uncharged nature, these colorants can diffuse into the nylon polymer structure to cause a stain. Betadine and mustard stains are often very difficult (and sometimes almost impossible) to clean because the stains are often very tenacious after diffusion of the staining agent into the nylon fiber.
Since traditional stainblocker chemicals are ineffective in preventing staining by disperse dyes, methods of addressing staining by mustard and Betadine have historically involved attempts to remove the stains after the fiber is stained. Quite often, these recommended methods and cleaning agents for removing mustard and Betadine stains can damage the color of dyed nylon fibers, therefore causing dye fading or other discoloration. Also, these treatments can remove the stainblocker from the surface of the fibers or reduce its effectiveness, thus making the nylon fibers more susceptible to staining with acid dyes or other materials at a later time. The effectiveness of other treatments such as water repellents and UV absorber applications can also be reduced or eliminated by cleaning agents used to remove staining by mustard and Betadine from nylon fibers after staining of the fibers.
Improved stain resistance after wet cleaning can be achieved by increasing the amount of a SAC stainblocker product initially applied to the substrate. However, this generally leads to discoloration caused by yellowing of the substrate at first application and further discoloration upon exposure to air and light.
A recent patent, U.S. Pat. No. 6,814,758, (the “'758 patent”), the disclosure of which is incorporated herein in its entirety by this reference, purports to impart Betadine resistance to nylon fibers. This patent states that the application of SAC in an amount greater than 2% wt/wt (weight dry SAC/weight dry nylon fiber) in a wet fixing process will provide a fiber that is resistant to staining by Betadine.
While that method may provide some resistance to staining by Betadine, the inventor herein has found that nylon fibers treated with the methods and compositions of the '758 patent still exhibit unacceptable staining by Betadine, as well as mustard. Indeed, it has been found by the inventor herein that the methods and compositions of the '758 patent do not provide Betadine, and mustard resistance as would be found acceptable in many commercial applications.
In light of the above, it would be desirable to identify methods and compositions to provide improved resistance to staining by disperse dyes, such as mustard and Betadine. Still further, it would be desirable to identify methods and compositions that would provide such resistance without undesirable yellowing caused by the application of high amounts of SAC-type stainblocker chemicals to the fibers. The present invention provides such improvements.